document.write( "Question 757381: I do not understant how to set up a rational equation for word probles such as this.
\n" ); document.write( "Debbie traveled by boat 5 miles upstream to fish. Because of the 4 mph current, it took her 40 minutes longer to get there than to return. How fast will her boat go in still water? \r
\n" ); document.write( "\n" ); document.write( "Could you please help me, thanks \n" ); document.write( "
Algebra.Com's Answer #460774 by stanbon(75887)\"\" \"About 
You can put this solution on YOUR website!
Debbie traveled by boat 5 miles upstream to fish. Because of the 4 mph current, it took her 40 minutes longer to get there than to return. How fast will her boat go in still water?
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\n" ); document.write( "Upstream DATA: distance = 5 miles ; rate = b-4 mph ; time = d/r = 5/(b-4)
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\n" ); document.write( "Downstream DATA: distance = 5 miles ; b+4 mph ; time = d/r = 5/(b+4)
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\n" ); document.write( "Equation:
\n" ); document.write( "up time - down time = 2/3 hrs.
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\n" ); document.write( "5/(b-4) - 5/(b+4) = 2/3
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\n" ); document.write( "Multiply thru by 3(b-4)(b+4) to get:
\n" ); document.write( "15(b+4) - 15(b-4) = 2(b^2-16)
\n" ); document.write( "60 + 60 = 2b^2-32
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\n" ); document.write( "60 = b^2 - 16
\n" ); document.write( "b^2 = 76
\n" ); document.write( "Positive solution:
\n" ); document.write( "b = 8.72 mph (speed of the boat in still water)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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